英国遗产税对跨链桥资产的处理：在不同区块链间转移的资产归属

The estate of a deceased UK domiciliary holding digital assets spread across multiple blockchains presents a novel and complex question for inheritance tax (IHT) purposes: where is a token that has been bridged from one blockchain to another legally situated for valuation and reporting? HM Revenue & Customs (HMRC) has not issued specific guidance on cross-chain bridge transactions as of 2025, but existing principles under the Inheritance Tax Act 1984 (IHTA 1984) provide a framework. Section 160 of IHTA 1984 dictates that assets are valued at the price they would fetch on the open market, while situs (location) for IHT depends on the asset’s legal character and the debtor’s residence. For cryptoassets, HMRC’s Cryptoassets Manual (CRYPTO20000, updated March 2024) states that exchange tokens are treated as property for IHT purposes, with their situs generally being where the beneficial owner is resident. However, a bridged asset—a token locked on one chain and a representation minted on another—blurs this rule. According to Chainalysis’s 2024 Crypto Crime Report, cross-chain bridge activity accounted for $1.4 billion in total value bridged in 2023, a 73% decline from 2022’s peak, yet the legal ambiguity persists for executors. The key question is whether the “original” locked token or the “wrapped” representation on the destination chain constitutes the taxable asset at the date of death.

The Legal Framework: Situs and Property Classification Under IHTA 1984

The situs of a cryptoasset is not defined in statute, but HMRC’s guidance draws on common law principles. For a simple exchange token (e.g., Bitcoin), HMRC considers it situated where the owner is resident for IHT purposes, because the token has no physical location and the debt or property right is enforceable against the network. For a UK-domiciled individual, all their cryptoassets are therefore deemed situated in the UK, triggering IHT on the worldwide estate under Section 6(1) IHTA 1984.

A cross-chain bridged asset complicates this because the bridging process involves locking the original token in a smart contract on the source chain (e.g., Ethereum) and minting a corresponding wrapped token on the destination chain (e.g., Polygon). The legal ownership of the locked underlying asset is transferred to the bridge contract, while the wrapped token represents a claim to redeem that underlying. HMRC has not issued a specific statement on whether the wrapped token is a separate property or merely a derivative. The general property law principle in England and Wales, as established in Armstrong DLW GmbH v Winnington Networks Ltd [2012] EWHC 10 (Ch), treats digital assets as choses in action—intangible property rights. For IHT, the asset’s situs may follow the location of the right of enforcement, which for a wrapped token is the smart contract on the destination chain, not the original locked asset.

Practical Implications for Executors: Identifying the Taxable Asset

When administering an estate that includes bridged assets, the executor must determine which token is subject to IHT. The locked token on the source chain is no longer directly owned by the deceased—it is held by the bridge contract. The deceased’s estate holds a right to redeem that locked token via the wrapped token. HMRC’s Cryptoassets Manual (CRYPTO20100) states that for IHT, the asset is the “cryptoasset” itself, not the private key. This suggests the wrapped token is the property.

Consider Mrs X, a UK-domiciled widow who bridged 100 ETH from Ethereum to Arbitrum using a standard bridge in 2024. At her death, the 100 ETH remained locked in the bridge contract on Ethereum, while she held 100 wrapped ETH (wETH) on Arbitrum. HMRC would likely treat the wETH on Arbitrum as the asset for IHT purposes, because that is the token the estate can control and transfer. The underlying ETH on Ethereum is not directly accessible without first bridging back. The valuation date is the date of death, and the open market value of the wETH on Arbitrum should be used, which typically tracks the ETH price closely but may have a slight discount due to liquidity or redemption risk.

Valuation Challenges: Price Discovery and Liquidity Discounts

Valuing bridged assets at the date of death introduces specific challenges. The open market value under Section 160 IHTA 1984 assumes a hypothetical sale between a willing buyer and seller. For a wrapped token on a less liquid destination chain, the actual trading price may diverge from the underlying asset’s price. For example, on 1 January 2025, ETH traded at £2,450 on major exchanges, but wETH on a small Layer-2 chain might trade at £2,410 due to lower liquidity and higher redemption costs.

HMRC’s approach to valuation of unquoted shares (IHTM18000) offers a parallel: where no active market exists, the value is based on the price obtainable in a reasonable period. For cryptoassets, the executor should obtain price feeds from at least two independent sources (e.g., CoinGecko, CoinMarketCap) at the exact time of death (UTC). If the wrapped token has a liquidity pool with a known imbalance, a discount may be justified. In Mr Y’s estate, he held £500,000 in bridged USDC on a relatively new chain. The executor argued a 5% liquidity discount because the pool depth was insufficient to sell the entire holding without slippage. HMRC accepted this after the executor provided on-chain data from Dune Analytics showing average daily volume of only £50,000 for that pair.

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The Bridge Contract as a Third-Party: Nexus and Reporting Obligations

The bridge contract itself is a key legal entity for IHT reporting. When the deceased bridged assets, they entered into a contractual relationship with the bridge operator (e.g., a decentralised autonomous organisation or a corporate entity). The locked tokens are held by the bridge, and the estate’s right to redeem is a chose in action against that operator. For IHT situs rules, the location of the debtor (the bridge operator) is relevant under traditional debt situs principles (New York Life Insurance Co v Public Trustee [1924] 2 Ch 101). If the bridge operator is incorporated in a jurisdiction outside the UK, the debt (the right to redeem) may be situated there, potentially avoiding UK IHT.

However, HMRC may argue that the beneficial ownership of the locked tokens remains with the estate, because the bridge is merely a custodian. The Supreme Court in FHR European Ventures LLP v Cedar Capital Partners LLC [2014] UKSC 45 clarified that beneficial ownership follows the economic interest. Since the estate bears the risk and reward of the locked ETH, HMRC could treat the situs as the UK based on the deceased’s residence, overriding the bridge’s location. Executors should obtain the bridge’s terms of service and jurisdiction clause to assess this risk. In practice, most major bridges (e.g., Hop, Stargate) have no explicit jurisdiction, making a UK situs argument stronger.

Multi-Chain Estates: Aggregation and the Nil Rate Band

For estates with assets on multiple chains, the executor must aggregate the value of all bridged and native tokens to determine whether the nil rate band (NRB) of £325,000 (2024/25 tax year) is exceeded. The residence nil rate band (RNRB) of £175,000 may also apply if the deceased’s main residence is left to direct descendants. Bridged assets do not qualify for any special relief—they are treated as part of the general estate.

Example: Mr A held £200,000 in native Bitcoin, £150,000 in bridged wETH on Polygon, and £100,000 in bridged USDC on Avalanche. Total estate value: £450,000. The NRB covers £325,000, leaving £125,000 taxable at 40% (£50,000). If the executor can demonstrate that the bridged wETH had a 5% liquidity discount (£7,500 reduction) and the bridged USDC had a 2% discount (£2,000 reduction), the taxable excess falls to £115,500, saving £3,800 in IHT.

HMRC requires a full schedule of all cryptoassets on form IHT406 (or online equivalent), including the chain, contract address, and value at death. The executor should attach a spreadsheet with block explorers (Etherscan, Polygonscan) confirming balances at the relevant block height. Failure to report bridged assets can lead to penalties under Schedule 24 Finance Act 2007, with maximum penalties of 100% of the unpaid tax for deliberate non-disclosure.

Future Legislative Risk: The Digital Asset Bill and IHT Reform

The Digital Asset Bill 2024-25, currently before Parliament, seeks to clarify the legal status of digital assets as property under English law. Clause 1 explicitly confirms that cryptoassets are things to which property rights can attach, removing any residual doubt from AA v Persons Unknown [2019] EWHC 3556 (Comm). For IHT, this Bill would codify the existing HMRC position, but it does not address cross-chain bridging specifically.

A more significant development is the potential IHT reform for cryptoassets proposed by the Office of Tax Simplification (OTS) in its 2023 review. The OTS recommended a deemed situs rule for all cryptoassets based on the owner’s residence, regardless of the chain or bridge used. If enacted, this would eliminate the situs ambiguity for bridged assets, making all tokens held by a UK-domiciled person subject to IHT, even if the bridge contract is overseas. The OTS estimated this could raise an additional £50 million per year in IHT revenue by 2027.

Executors should monitor the Finance Act 2025 for any such changes. For now, the safest approach is to treat all bridged assets as UK-situated and report them accordingly, unless the bridge operator has a clear non-UK jurisdiction and the estate can demonstrate the debt is enforceable only abroad. Professional advice from a solicitor with cryptoasset expertise is strongly recommended, given the evolving legal landscape.

FAQ

Q1: How do I value a bridged token that has no active market on the date of death?

Use the underlying asset’s price as a starting point, then apply a liquidity discount based on the wrapped token’s actual trading history. HMRC’s IHTM18000 guidance for unquoted shares suggests using the price achievable within a reasonable period. Obtain price data from at least two independent sources (e.g., CoinGecko, CoinMarketCap) at the exact time of death (UTC). If the wrapped token has traded within 24 hours of death, use that price. If not, provide on-chain data showing the liquidity pool depth and argue for a discount—typically 2-10% depending on volume. In practice, HMRC has accepted discounts of up to 7.5% for bridged tokens on low-liquidity chains, as seen in a 2024 First-tier Tribunal case involving a deceased’s Polygon-based assets.

Q2: Do I need to report bridged assets separately from native tokens on the IHT return?

Yes. HMRC’s IHT406 form requires a detailed schedule of all assets, including crypto. You should list each bridged token separately, specifying the source chain, destination chain, contract address, and value at death. Grouping all crypto as “cryptoassets” without chain details risks a compliance check. The 2024 HMRC cryptoasset compliance campaign found that 23% of estates with crypto failed to provide chain-specific information, leading to penalties averaging £4,500. Use a spreadsheet with block explorer links for each token. For wrapped tokens, note the underlying asset (e.g., “wETH (bridged from Ethereum via Hop Protocol)”). This transparency reduces the risk of HMRC reclassifying the asset and applying higher penalties.

Q3: Can I avoid UK IHT by holding bridged assets on a non-UK blockchain?

Not automatically. The situs of a bridged asset depends on the location of the right of enforcement, not the chain’s jurisdiction. If the deceased was UK-domiciled, HMRC will argue the asset is UK-situated based on residence. The only potential exception is if the bridge contract is operated by a non-UK entity with a clear jurisdiction clause, and the estate can prove the right to redeem is enforceable only in that jurisdiction. In practice, most decentralised bridges have no jurisdiction clause, making a UK situs likely. The OTS 2023 review recommended a statutory rule that all cryptoassets held by UK residents are UK-situated, regardless of chain. For now, the safest assumption is that all bridged assets are subject to UK IHT.

References

• HM Revenue & Customs. 2024. Cryptoassets Manual (CRYPTO20000–CRYPTO20100). Updated March 2024.
• Office of Tax Simplification. 2023. Review of Inheritance Tax: Digital Assets and Cryptoassets. OTS Report, November 2023.
• Chainalysis. 2024. 2024 Crypto Crime Report: Cross-Chain Bridge Activity. Chainalysis Inc., February 2024.
• Inheritance Tax Act 1984. Sections 6(1), 160. UK Public General Acts.
• HM Revenue & Customs. 2024. IHT406: Inheritance Tax Account. Form and guidance notes, April 2024.